Urosepticemia and fatal endocarditis caused by aerococcus-like organisms

Aerococcus urinae: A Rare Cause of Endocarditis Presenting With Acute Stroke

Aerococcus urinae is a rare organism infrequently isolated from cultures. Mostly known to cause urinary tract infection, it can cause bacteremia leading to severe urosepsis and infective endocarditis. Embolization is frequently reported with Aerococcus urinae endocarditis (AUE); hence, the presentation is highly variable. Sequelae such as various central nervous system manifestations, sepsis, valvular regurgitation with heart failure and even coronary artery involvement have been reported. We report a case of a 58-year-old man with AUE of the aortic valve, severe aortic regurgitation and embolic stroke as a result of embolization from AUE and ultimately required aortic valve replacement. Our case highlights this rare cause of endocarditis and offers insight into the variability of patient presentation and risk factors to consider.

Aerococcus urinae - A potent biofilm builder in endocarditis

The diagnosis of infective endocarditis (IE) remains a challenge. One of the rare bacterial species recently associated with biofilms and negative cultures in infective endocarditis is Aerococcus urinae. Whether the low number of reported cases might be due to lack of awareness and misidentification, mainly as streptococci, is currently being discussed. To verify the relevance and biofilm potential of Aerococcus in endocarditis, we used fluorescence in situ hybridization to visualize the microorganisms within the heart valve tissue. We designed and optimized a specific FISH probe (AURI) for in situ visualization and identification of A. urinae in sections of heart valves from two IE patients whose 16S rRNA gene sequencing had deteced A. urinae. Both patients had a history of urinary tract infections. FISH visualized impressive in vivo grown biofilms in IE, thus confirming the potential of A. urinae as a biofilm pathogen. In both cases, FISH/PCR was the only method to unequivocally identify A. urinae as the only causative pathogen for IE. The specific FISH assay for A. urinae is now available for further application in research and diagnostics. A. urinae should be considered in endocarditis patients with a history of urinary tract infections. These findings support the biofilm potential of A. urinae as a virulence factor and are meant to raise the awareness of this pathogen.

Aerococcus urinae Mitral Valve Endocarditis-Related Stroke: A Case Report and Literature Review

Background. Aerococcus urinae is a rare causative pathogen of infective endocarditis that results in a high risk of embolic events. The mortality rate for A urinae endocarditis is high. Old age and underlying urologic conditions are the best-known risk factors for infection. Case Description. We report the clinical course of the disease in a 49-year-old man who presented symptoms of a urinary tract infection. A few days later, transthoracic echocardiography showed a conspicuous mitral valve with myxomatous alterations. Following the detection of a cerebral embolism with associated stroke symptoms, as well as at the beginning of cardiac failure, the emergency indication for the surgical treatment of mitral valve endocarditis was given. On the second day following the operation, circulatory collapse rapidly developed. Following an unsuccessful attempt at cardiopulmonary resuscitation, the patient died. Review of the Literature. From 1991 to 2017, 29 cases of A urinae–induced endocarditis have been described in PubMed and Medline. One or 2 new cases are published annually. We review all reported cases of A urinae endocarditis, with an emphasis on the predisposing factors, course, and outcomes of the disease. Conclusion. A urinae endocarditis is a rare disease primarily affecting elderly men with urinary tract pathologies and comorbidities. The course of the disease is severe, and the outcome is often fatal. A 16S rDNA polymerase chain reaction investigation of bacterial genome provides proof of the presence of A urinae. Because of the high risk of embolism, rapid treatment should focus on the diseased heart valve. Based on existing data and the experience gained from handling cases, treatment with β-lactam and aminoglycosides is recommended. It is also recommended that operative therapy take place as soon as possible.

Gram-Positive Uropathogens, Polymicrobial Urinary Tract Infection, and the Emerging Microbiota of the Urinary Tract

Gram-positive bacteria are a common cause of urinary-tract infection (UTI), particularly among individuals who are elderly, pregnant, or who have other risk factors for UTI. Here we review the epidemiology, virulence mechanisms, and host response to the most frequently isolated Gram-positive uropathogens: Staphylococcus saprophyticus, Enterococcus faecalis, and Streptococcus agalactiae. We also review several emerging, rare, misclassified, and otherwise underreported Gram-positive pathogens of the urinary tract including Aerococcus, Corynebacterium, Actinobaculum, and Gardnerella. The literature strongly suggests that urologic diseases involving Gram-positive bacteria may be easily overlooked due to limited culture-based assays typically utilized for urine in hospital microbiology laboratories. Some UTIs are polymicrobial in nature, often involving one or more Gram-positive bacteria. We herein review the risk factors and recent evidence for mechanisms of bacterial synergy in experimental models of polymicrobial UTI. Recent experimental data has demonstrated that, despite being cleared quickly from the bladder, some Gram-positive bacteria can impact pathogenic outcomes of co-infecting organisms. When taken together, the available evidence argues that Gram-positive bacteria are important uropathogens in their own right, but that some can be easily overlooked because they are missed by routine diagnostic methods. Finally, a growing body of evidence demonstrates that a surprising variety of fastidious Gram-positive bacteria may either reside in or be regularly exposed to the urinary tract and further suggests that their presence is widespread among women, as well as men. Experimental studies in this area are needed; however, there is a growing appreciation that the composition of bacteria found in the bladder could be a potentially important determinant in urologic disease, including susceptibility to UTI.

Epidemiology and antibiotic susceptibility of aerococci in urinary cultures

In this study, we present population-based data regarding the prevalence of aerococci in clinical urinary samples. During a 3-month period, all aerococcal isolates from urinary samples from 2 clinical microbiology laboratories were collected. We identified 64 Aerococcus urinae isolates and 40 Aerococcus sanguinicola isolates, which correlates with an incidence of 33 cases of aerococcal bacteriuria per 100,000 inhabitants per year. The median age was 83years for all patients with aerococcal bacteriuria, which was significantly higher than for patients with Escherichia coli or Enterococcus faecalis bacteriuria. Sex was almost equally distributed between men and women with aerococcal bacteriuria, whereas females dominated in E. coli bacteriuria. The aerococcal isolates displayed low MICs for ampicillin, cefalotin, mecillinam, and nitrofurantoin. Most A. sanguinicola isolates were resistant to ciprofloxacin, whereas most A. urinae isolates had low MICs. Clinical studies are needed to establish clinical breakpoints and optimal treatment.

Aerococci and aerococcal infections

Aerococcus is a genus that comprises seven species, of which Aerococcus urinae, and Aerococcus sanguinicola are emerging human pathogens. Aerococci are gram positive cocci that are easily misidentified as streptococci or staphylococci, and thus the incidence of aerococcal infections has been underestimated. With the introduction of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) clinical microbiologists now have access to a rapid and accurate method to identify aerococci. A. urinae and A. sanguinicola are isolated in a small proportion of urinary specimens in many laboratories and many patients with bacteriuria with aerococci have symptoms of urinary tract infection (UTI). A. urinae, and also A. sanguinicola, cause invasive infections including infective endocarditis (IE) with many reported fatalities. Especially older men with urinary tract abnormalities are at risk for bacteraemia with A. urinae but the prognosis of bacteraemia without IE is favourable. Penicillin is appropriate for treatment of invasive infections and in IE, addition of an aminoglycoside should be considered. Treatment of UTI with aerococci is complicated by uncertainty about the effect of trimethoprim-sulphametoxazole and fluoroquinolones on aerococci. This review will discuss identification of Aerococcus spp., antibiotic resistance, the clinical presentation and management of aerococcal infections as well as the virulence mechanisms of these bacteria.

[A case of infective Aerococcus urinae endocarditis successfully treated by aortic valve replacement]

Aerococcus urinae is a endocarditis rare causative organism with low virulene. We report an A. urinae endocarditis case treated by aortic valve replacement. An 80-year-old woman hospitalized for urinary tract infection and hydronephrosis due to three-week renal calculi. Blood culture on admission isolated Streptococcus acidominimus. During the course, she was transferred to our care for surgical intervention after developing congestive heart failure due to severe aortic regurgitation. Echocardiographic findings indicated infective endocarditis. She underwent aortic valve replacement, and gram staining of the resected valve tissue showed gram-positive cocci, although valve culture was negative. PCR amplification and DNA sequencing using the valve material matched an A. urinae sequence. The woman recovered and was discharged six weeks after antibiotic treatment.

Comparative molecular and microbiological diagnosis of 19 infective endocarditis cases in which causative microbes were identified by PCR-based DNA sequencing from the excised heart valves

Infective endocarditis (IE) is traditionally diagnosed by microbiological analysis of blood cultures, following which therapeutic antibiotics are chosen based on antimicrobial sensitivity tests. However, such conventional techniques do not always lead to an accurate etiological diagnosis. Recently, PCR analysis of the 16S rRNA gene has been employed to identify organisms isolated from excised heart valves. In this study, we analyzed 19 valve samples from patients with confirmed IE, as identified by Duke's criteria. Using broad-range PCR amplification, followed by direct gene sequencing, pathological agents were identified in all samples. Although blood cultures yielded negative results in 4 cases, PCR analysis of valve samples showed positive identification of causative organisms. In 3 cases, there was a difference between blood culture and PCR in identification of pathological agents, which are likely to be misidentified by the conventional method based on the phenotypic database. Postoperative antibiotics were chosen considering the severity of lesions and the results of PCR, Gram staining, and valve cultures. All patients were cured without relapse. The broad-range PCR method was therefore beneficial for the management of IE because it enabled us to identify pathogens directly from the site of infection, even organisms that were difficult to culture or likely to be misidentified by the conventional culture method. Identification of the agents provided precise knowledge of the microbiological spectrum involved in the cases of IE.

Clinical and microbiological features of bacteraemia with Aerococcus urinae

Aerococcus urinae is a Gram-positive bacterium that can cause invasive infection, including infectious endocarditis (IE), mainly in older men. A. urinae is often misclassified in routine diagnostic laboratories. Through searches in the laboratory databases we identify 16 isolates of A. urinae causing bacteraemia during a 6-year period in southern Sweden, indicating that bacteraemia with A. urinae occurs in at least three cases per million inhabitants per year. The identity of isolates was confirmed by sequencing of the 16S rRNA genes and antibiotic susceptibility testing identified two ciprofloxacin-resistant isolates. A. urinae was the only significant pathogen isolated in all cases. Fifteen of the 16 patients were male, 15/16 were more than 70 years old, and 12/16 had underlying urological conditions. Though a urinary tract focus was suspected in the majority of cases, the bacterium was rarely found in urinary samples. Nine patients fulfilled the criteria for severe sepsis and an additional four fulfilled the criteria for sepsis. Only one fatality was recorded. Patients were treated mainly with beta-lactam antibiotics but fluoroquinolones and clindamycin were also used. Three cases of IE were diagnosed and these were complicated by spondylodiscitis in one case and by septic embolization to the brain in one case. An increased awareness of A. urinae is crucial to establishing its role as an important pathogen in older men with urinary tract disease.

Platelet activation and biofilm formation by Aerococcus urinae, an endocarditis-causing pathogen

The Gram-positive bacterium Aerococcus urinae can cause infectious endocarditis (IE) in older persons. Biofilm formation and platelet aggregation are believed to contribute to bacterial virulence in IE. Five A. urinae isolates from human blood were shown to form biofilms in vitro, and biofilm formation was enhanced by the presence of human plasma. Four of the A. urinae isolates caused platelet aggregation in platelet-rich plasma from healthy donors. The Au3 isolate, which induced platelet aggregation in all donors, also activated platelets, as determined by flow cytometry. Platelet aggregation was dependent on bacterial protein structures and on platelet activation since it was sensitive to both trypsin and prostaglandin E(1). Plasma proteins at the bacterial surface were needed for platelet aggregation; and roles of the complement system, fibrinogen, and immunoglobulin G were demonstrated. Complement-depleted serum was unable to support platelet aggregation by Au3 and complement blockade using compstatin-inhibited platelet activation. Platelet activation by Au3 was inhibited by blocking of the platelet fibrinogen receptor, and this isolate was also shown to bind to radiolabeled fibrinogen. Removal of IgG from platelet-rich plasma by a specific protease inhibited the platelet aggregation induced by A. urinae, and blockade of the platelet FcRγIIa hindered platelet activation induced by Au3. Convalescent-phase serum from a patient with A. urinae IE transferred the ability of the bacterium to aggregate platelets in an otherwise nonresponsive donor. Our results show that A. urinae exhibits virulence strategies of importance for IE.

Fatal infective endocarditis due to Aerococcus urinae--case report and review of literature

Aerococcus-related infective endocarditis is a rare form of endocarditis with a high mortality. Most cases have associated genitourinary system pathology. Aerococcus urinae is a Gram-positive coccus that is arranged in clusters resembling Staphylococcus, but its growth characteristics and colonial morphology are closer to that of an alpha-hemolytic Streptococcus. This organism may initially be dismissed as a contaminant in clinical cultures from nonsterile sites. We report a representative case and review the literature concerning this unusual case of infective endocarditis.

Clinical significance of Aerococcus urinae: a retrospective review

A retrospective chart review was performed on 54 patients with positive urine cultures during a 1-year period to assess the clinical significance of Aerococcus urinae. Based on predetermined criteria, patients were classified into 2 groups: those with urinary tract infections (UTIs) and those who were considered colonized. The majority of the patients were > or =65 years old and were female. Only 31% of patients with UTI and 45% of colonized patients had A. urinae isolated in pure cultures. Both groups had significant but similar underlying medical conditions, with urologic conditions being predominant. Significantly more patients in the UTI group had urinary catheters (P < .01). No direct complications or invasive disease was recognized in either group regardless of whether patients were treated with antibiotics. Apparently, A. urinae is a relatively avirulent organism when cultured from urine.

Aerococcus urinae: polyphasic characterization of the species

A polyphasic characterization of Aerococcus urinae is presented. In this study the intraspecies relationships between 26 strains of varying geographical origin were examined by phenotypic tests, ribotyping and multilocus enzyme electrophoresis. The results demonstrated two main phenotypic patterns that could be distinguished in tests for hydrolysis of aesculin, and acid production from amygdalin and salicin. Strains were either negative (n=19) or positive (n=6) in these tests. One strain had a deviating pattern. Heterogeneity within the 19 pattern I strains was demonstrated especially by phenotypic tests (acid production from ribose, mannitol, sorbitol, sucrose and D-arabitol) and by multilocus enzyme electrophoresis. However, DNA sequence analysis of the 16S rRNA (n=7) and gyrB genes (n=3) from strains representing the two main patterns showed no variation in sequences among strains. Comparison of A. urinae and representatives of related taxa by 16S rDNA sequence analysis showed that the taxon is related to, but distinct from, other Aerococcus spp.

Aerococcus urinae in urinary tract infections

Aerococcus urinae is a rarely reported pathogen, possibly due to difficulties in the identification of the organism. A. urinae is a gram-positive coccus that grows in pairs and clusters, produces alpha-hemolysis on blood agar, and is negative for catalase and pyrrolidonyl aminopeptidase. Some of these characteristics and its being absent from the databases of most commercial identification systems could allow A. urinae to be misidentified as a streptococcus, enterococcus, or staphylococcus. We report two cases of urinary tract infection (UTI) caused by A. urinae and characterize these isolates by morphology, biochemical testing, whole-cell fatty acid analysis, 16S rRNA gene sequencing, and antibiotic susceptibilities. Most patients infected with A. urinae are elderly males with predisposing conditions who present initially with UTI. Because A. urinae is resistant to sulfonamides, treatment could be inappropriate, with infections resulting in serious complications, including death. It is important for the clinician and the microbiologist to consider A. urinae a potential pathogen and proceed with thorough microbiological identification.

Identification, classification, and clinical relevance of catalase-negative, gram-positive cocci, excluding the streptococci and enterococci

Several new genera and species of gram-positive, catalase-negative cocci that can cause infections in humans have been described. Although these bacteria were isolated in the clinical laboratory, they were considered nonpathogenic culture contaminants and were not thought to be the cause of any diseases. Isolation of pure cultures of these bacteria from normally sterile sites has led to the conclusion that these bacteria can be an infrequent cause of infection. This review describes the new bacteria and the procedures useful for clinical laboratories to aid in their identification. The clinical relevance and our experience with the various genera and species are reviewed and discussed.

Fatal endocarditis due to Aerococcus urinae

Aerococcus species are Gram-positive cocci having Gram-stain characteristics of staphylococci (i.e., form clusters), but biochemical and growth characteristics resembling streptococci and enterococci (i.e., catalase-negative, alpha-hemolytic growth on blood agar). A case of fatal endocarditis due to Aerococcus urinae is presented. Endocarditis should be suspected and, if confirmed, treated aggressively when A. urinae is recovered from blood cultures.

Endocarditis caused by Aerococcus urinae, a newly recognized pathogen

Aerococcus urinae is a newly described pathogen. A case of Aerococcus urinae endocarditis is presented, the primary focus being a urinary tract infection. The diagnosis of endocarditis was supported by isolation of Aerococcus urinae from blood as well as from heart vegetations.

Septicaemia due to Aerococcus urinae

In a case of septicaemia, Aerococcus urinae was isolated from the blood. The patient had undergone operation on the prostate gland. The urine was sterile.

Crossed immunoelectrophoresis used for bacteriological diagnosis in patients with endocarditis

Sera from 151 patients suspected of having endocarditis were obtained during a period of 3 1/2 years at Rigshospitalet, Copenhagen. The sera were examined by crossed immunoelectrophoresis for antibodies to bacteria causing endocarditis. The patients were divided into four groups: 1. Patients with definite endocarditis, 2. Patients with culture-negative endocarditis, 3. Patients with uncertain endocarditis, and 4. Patients without endocarditis. In sera from patients suffering from endocarditis caused by viridans streptococci, precipitating antibodies were demonstrated by crossed immunoelectrophoresis (diagnostic specificity = 86%; diagnostic sensitivity = 100%) while other bacterial etiologies of endocarditis were less reliably demonstrated by this method.